\section{Asymmetric Information} \label{asymmetricInfo}
Before looking into available technologies, it is important to examine the theory behind asymmetric information.

This section is based on the chapter \textit{Patterns for Information, Communication, Presentation} from the book \textit{Patterns in Game Design} by \citep{patternsInGameDesign}. Before asymmetric information is explained, the concepts of imperfect information and uncertainty of information will be defined.

\subsection{Imperfect Information} \label{imperfectInfo}
\citep{patternsInGameDesign} define \textit{imperfect information} as when \textit{"One aspect of information about the total game situation is not fully known to a player, either the information known is totally wrong or the accuracy of the information is limited."} Players can either lack information or have faulty information.

\textit{Lack of information} is for instance used in card games where players might know which cards are in the deck, but not which cards other players have in their hands, bringing a strategic element to the game. Another typical use is to set up so-called \textit{gain information goals}, where for instance the player knows that he needs to find a princess, but without knowing where the princess is. The location of the princess is therefore the imperfect information, and finding her is the goal.

\textit{Faulty information} is when a player receives incorrect information and is mostly used to allow players to mislead or distract their opponents by setting up \textit{red herrings} or \textit{bluffing}. This is for instance seen in the game poker where players are encouraged to deceive each other. 

Imperfect information is also used to create anticipation for the player by limiting the player's planning ability, causing him to resort to leap of faith decisions. This is called \textit{limited foresight}. Examples of this can be seen in fast-paced action games, where the speed of the gameplay limits the players in analyzing the situation and planning ahead. 

To allow replayability with imperfect information, games can avoid revealing the imperfect information at the end of the game. This way, player strategies are not revealed, and overlooked goals or paths might bring the player back to the game. Replayability can also be added by having \textit{dynamic goal characteristics}, which means that the imperfect information randomly changes between game instances.

\subsection{Uncertainty of Information}
\citep{patternsInGameDesign} also talk about \textit{uncertainty of information} and how it is tightly connected to imperfect information. Uncertainty of information deals with the level of reliability of the information players possess. Depending on the manner in which the player receives information, he cannot always trust it. Especially when the game relies on \textit{indirect information}, meaning that the \textit{direct information} has been translated or distorted (by a third party such as a person or a machine), uncertainty of information is unavoidable.

As soon as a game gives players asymmetric information and allows them to negotiate in some way, the game supports uncertainty of information, since \citep{patternsInGameDesign} state that players themselves can be an unreliable medium. This can for instance be seen in poker, where uncertain information is mediated through social interactions/observations between players, making body language an important factor. Uncertain information can also be communicated through mechanics of the game, where the game can provide players inaccurate information.

Finally, \citep{patternsInGameDesign} define uncertainty of information as an element that can increase tension or encourage randomness, since the players can be forced to make important decisions without being fully aware of the consequences.

\subsection{Asymmetric Information} \label{ass}
\citep{patternsInGameDesign} define \textit{asymmetric information} as a type of information distribution to players where \textit{"Players have different information available to them, i.e., some players know more than other players."} In opposition to \textit{symmetric information}, asymmetric information requires that at least one of the players has imperfect information.

Asymmetric information can be balanced between players such as in poker, where each player has imperfect information about what all the other players have in their hands. This can also be referred to as \textit{potential symmetric information} in that all players can potentially figure out the distribution of cards by analyzing actions and events throughout the game.

It can, however, also be unbalanced such as in the word-guessing game charades, where one of the players knows the answer and therefore has perfect information, while the other players need to guess the answer and therefore have imperfect information. Indirect information is used in charades by making the player with perfect information give the answer to the other players non-verbally, even though the answer is a written sentence.

In the example of poker, asymmetric information is used to preserve secret resources by letting players have their cards in their hands. Asymmetric information can also be used to distribute specific goals secretly to players such as in the board game The Resistance. In this game, some players are secretly told that they are on the "good" team, while others are told they are on the "evil" team. Each team has its own goals, and players reach the goals exclusively through negotiation. This game is also an example of how asymmetric information can be used across teams, since the "evil" team has knowledge about which teams all players are on, while the "good" team does not. 

\subsection{Communication Channels} \label{kommunist}
To further work with asymmetric information, it is important to understand the different channels that players can use to pass information to each other. \citep{patternsInGameDesign} define communication channels with the following sentence: \textit{"Communication Channels are the medium and the methods players can use to send messages to other players."} Furthermore, they compare some different situations in which communication channels are used: face-to-face versus mediated; synchronous versus asynchronous; and verbal versus non-verbal.

In face-to-face situations, non-verbal communication such as gestures or facial expressions are commonly used and allow for gameplay that relies on this. In opposition, when communication is mediated, the players are not necessarily sharing the same physical location. For instance, online games allow players to communicate through Voice over IP \citep{voip}.

Synchronous communication means that there is no delay in communication, whereas asynchronous communication means that there is a delay. Face-to-face communication induces synchronous communication, and mediated communication induces asynchronous communication.

Verbal communication means using a shared language for messages,  while non-verbal communication means using gestures and facial expressions through face-to-face communication or even drawings and animations through mediated communication. \citep{patternsInGameDesign} also mention that the most interesting situations happen when there is a possibility for verbal and non-verbal communication. 
